Here's another vote for side-by-side. I find it useful to have a 24" monitor in front of me as main display, which is also useful for graphics etc. to one side is a 15", which is mostly for emails and stuff to cut-and-paste. I agree also with the comments about a too-big monitor. For text, even the 24" is too big, at the distance I have it on my desk. More eye movement; more eyestrain. So I tend to have documents I'm working with in a smaller window in front of me. Horses for courses, however...